42 JUNE 2025 • WORLD AQUACULTURE • WWW.WAS.ORG and/or filter feeders may be one approach. Another challenge with open water is public perception. In many cases, neighbors have complained that views are impaired. This and other ‘social’ challenges may require education and outreach, but can also be partially ameliorated by minimizing the impact of emplacements on views — moving further offshore, minimizing visibility of components at the surface. Possibly adding a ‘green’ component to the system may help enhance public perception. Where water can be captured before release, constructed wetlands using coastal marine plant species (e.g. Juncus sp, Spartina alterniflora, Distichus spicata, Figure 6) can help reduce nutrients and grow plants with coastal restoration value. Systems like this may be expanded to constructed wetlands at large scale, enabling treatment of marine raceway effluents. Combinations of plants may be shown to be effective in overall nutrient uptake. In more open systems, filter feeders such as oysters can be grown for their valuable protein but may also help provide habitat, filter water and enhance water quality. If grown in combination with algae or coastal plants, these can help minimize impacts of open marine aquaculture and in some cases provide both ecological and economic benefits. Conclusions: Ongoing Challenges and Growing Opportunities in Marine Aquaponics Marine aquaculture is growing. Finding ways to avoid releasing nutrients and enhance value via plants and other species can be done with marine aquaponics. Unique challenges include salt impacts on plants. However, a growing array of plants are being used that are salt tolerant or salt loving halophytes. These include species for human food, coastal restoration, animal feeds and biofuels. Continued research is needed to optimize and expand these options for commercial producers, but these show great promise. Economic and ecological advantages as well as food and biofuels may be useful results of marine aquaponics. Ecosystem services in open systems can include enhanced habitat, as well as nutrient and carbon sequestration. FIGURE 5. Left) Salicornia is a true halophyte, preferring salinities of 10-30 ppt. Right) Duckweed can double in biomass in 3-4 days and can tolerate brackish waters. Duckweed can be effective in uptake of phosphorus (photos S.Hall, C. Pascual). Marine aquaculture is growing. Finding ways to avoid releasing nutrients and enhance value via plants and other species can be done with marine aquaponics. Unique challenges include salt impacts on plants. However, a growing array of plants are being used that are salt tolerant or salt loving halophytes. These include species for human food, coastal restoration, animal feeds and biofuels.
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